1. Field of the Invention
The present invention relates to a composition for thermosetting organic polymeric gate insulating layer and an organic thin film transistor using the same, and more particularly, to a composition for thermosetting organic polymeric gate insulating layer containing a thermosetting material in polyvinyl phenol as a material of organic polymeric gate insulating layer, to improve a chemical resistance and an insulating property, and an organic thin film transistor using the same.
2. Discussion of Related Art
In general, in an organic semiconductor field, after a conjugated organic polymer, such as polyacetylene, exhibiting a semiconductor property has been developed, active researches have been conducted in a wide range of functional electronic devices, optical devices etc. that serve as new electrical and electronic materials due to various advantages of the organic material which has not been obtained from an existing non-organic semiconductor material such as amorphous silicon or poly silicon, for example the diversity of synthetic methods, ease of forming into fiber or film shapes, flexibility, conductivity, and an inexpensive cost of production.
The researches on devices using these conductive polymers, particularly on an organic thin film transistor (TFT) using the organic material as an active layer have begun since 1980s. Currently, many researches are carried out all over the world.
The organic TFT is almost similar to a Si-TFT in structure, but it has a difference in that it makes use of the organic material instead of Si in a semiconductor region. The organic TFT has advantages capable of forming a thin film by means of an atmospheric pressure wet process (a printing coating process, a spin coating process, a bar coating process, or so forth) instead of a plasma enhanced chemical vapor deposition (CVD) for forming an existing Si-based thin film, and furthermore of realizing an inexpensive transistor by the aid of a roll-to-roll process using a plastic substrate.
It is currently expected that the organic TFT will be applied to a driving device of a plastic-based active organic electroluminescent display, a smart card, a plastic chip for inventory tags.
The organic TFT undergoes a performance test by means of electric charge mobility, on-off ratio, threshold voltage etc., and approaches an a—Si TFT in performance. Further, the performance of the organic TFT is influenced by a degree of crystallinity of an organic active layer, an interfacial charge characteristic between an organic insulating layer and an organic active layer, a thin film characteristic of the organic insulating layer, carrier injecting capability of interfaces between source and drain electrodes and the organic active layer, and so forth. In order to improve these characteristics, various methods have been attempted.
In particular, the use of a gate insulating layer of the organic TFT requires a material having low electrical conductivity and good breakdown field characteristic. The organic polymeric gate insulating layer that has been in use up to now includes polyimide (Korean Patent Publication No. 2003-0016981), polyvinyl alcohol (Korean Patent Publication No. 2002-0084427), poly(vinylphenol-maleimide) (Korean Patent Publication No. 2004-0028010), photoacryl, and so forth, but it has not shown enough characteristic to substitute an existing non-organic insulating layer. The non-organic insulating layer is formed at a high temperature. As such, when the non-organic insulating layer is applied to the organic TFT, it may have an influence on physical/chemical properties of an employed substrate (particularly, a plastic substrate) and another layer formed on a substrate in the previous process (hereinafter, referred to as a “prior process layer”), thus influencing the characteristics of the transistor.
Therefore, in order to realize the high-performance organic TFT, there is an acute need for development of the organic active layer material as well as the organic gate insulating layer that can be formed by a simplified process without having an influence on the substrate and the prior process layer (another layer formed on the substrate) and which is excellent in device property.
In this regard, the present inventors have found that, while they continue the research on the organic polymeric gate insulating layer for realizing the organic TFT at a high efficiency, a layer capable of improving a chemical resistance and an insulating property can be formed when a thermosetting material is included in the gate insulating layer material such as polyvinyl phenol and the device property can be improved when such a layer is employed to the organic TFT, and they completed the present invention.